Rapid charge interface enables faster smartphone battery charging

January 21, 2014 //
By Graham Prophet

Dialog Semiconductor has collaborated with Qualcomm Technologies to develop higher efficiency rapid smartphone charging; the Qualcomm Quick Charge 2.0-compatible AC/DC adapter enables up to 88% efficiency for high power density, rapid charge power supplies up to 40W.

The iW620 rapid charge interface IC resides on the secondary side of the AC/DC charger power supply and works with Dialog’s iW1760 PrimAccurate primary-side digital pulse width modulation (PWM) controller. Efficiency as high as 88% enables the higher power density needed for smaller form-factor fast charging adapters. Quick Charge 2.0 is a proprietary protocol from Qualcomm Technlogies, for charging smartphones, tablets and other mobile devices up to 75% faster than conventional USB charging technology.

Dialog’s Quick Charge 2.0 rapid charge AC/DC adapter solution delivers high efficiency up to 83% without the need for a synchronous rectifier that Dialog says is required by competing solutions. If a synchronous rectifier is used, it can achieve higher efficiency of up to 88%.

Current sensing is performed by the iW1760 on the primary side, eliminating the need for a secondary-side current sense resistor for a more efficient solution than competing Quick Charge 2.0 wall charger approaches. Primary-side current control also enables low cost implementation of different constant current thresholds for each output voltage.

The iW620 ensures safe operation with programmable, patented active fast output voltage discharge from 9V or 12V down to 5V. So, when the USB cable is unplugged from a Quick Charge 2.0 phone and then used with a non-Quick Charge 2.0 phone, the iW620 rapidly discharges the output voltage down to 5V, to protect the phone from damage.